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Program description - Helicopter mixer
Fine-tuning the throttle and collective pitch curve
Practical approach
Although the throttle and collective pitch control sys-
tems are based on separate servos, they are always
operated together by the throttle/pitch stick (except
during autorotation flight). This coupling is performed
by the helicopter program automatically.
In principle, the trim lever for control function 1 only
affects the throttle servo in the programs of the
mc-
16 HoTT and mc-20 HoTT transmitters – with the
exception of the choice of “PT” in the “Throttle” line of
the »Stick mode« menu, page 110, which is available
on the mc-20 HoTT transmitter only. This »Stick
mode« menu also enables you to define whether the
trim lever of control function 1 is to be used as part of
the throttle limiter function (“GA”), or for idle trimming
during auto-rotation exercises (“AR”).
The process of fine-tuning throttle and collective pitch,
i. e. setting the motor power curve to match the col-
lective blade pitch setting, is the most important as-
pect of setting up a model helicopter. The software of
the transmitters
mc-16 HoTT and mc-20 HoTT
provides for independent configuration of the throttle,
collective pitch and torque compensation curves, in
addition to the C1 control curve (»Channel 1 curve«
menu, page 137).
While these curves can be modelled using up to six
points, fewer points are generally sufficient. We re-
commend starting with three-point curves to begin
with. This involves setting individual values for the
centre point and other (optional) reference points, and
for the two end-points (“L”, “low”, and “H”, “high”) of
the throttle/collective pitch stick: together, these define
the control curves.
Before setting the throttle and collective pitch function,
the rods of all servos should be mechanically pre-ad-
justed correctly according to the set-up instructions for
the given helicopter.
Note:
The hover point should normally be set to
the centre position of the throttle / collec-
tive pitch stick. In special cases, e. g. for
“3D” ight, deviating hover points can also be
programmed. For example, one point for normal
ight attitude above the centre and one point for
inverted ight attitude below the centre.
Idle setting and throttle curve
Note:
Since electric drive systems have no need for
an idle setting, motor idling does not need to
be calibrated. Fine-tuning of the throttle and
collective pitch curve(s), however, must take place as
for glow-powered helicopters.
The idle setting, whose detailed description begins on
page 123, always takes place with the throttle limiter
closed – normally with the trim lever of the C1 function
and only in special cases is the throttle limiter itself also
utilized (as standard, the right-sided proportional rotary
slider (Lv2)).
The programming of a corresponding value for the
“L” point of the throttle curve acts to set the descent
speed of the motor, without influencing the hover con-
figuration.
Here, for example, flight phase programming can be
used to set different throttle curves. This increased sys-
tem rotational speed below the hover point proves to
be useful in certain circumstances, e. g. for fast, steep
landing approaches with greatly reduced collective
pitch, and for aerobatics.
The figure depicts a curve with a
slightly changeable throttle setting
below the hover point at the control
centre.
+100%
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OUTPUT
2 3 4 51
Control travel
Different throttle curves are programmed to be flight-
phase dependent in order to achieve the given optimal
adaptation to hovering flight as well as aerobatics:
• Low system rotational speed with smooth, gentle
control response and low noise when hovering
• Higher rotor speed for aerobatics with motor power
set close to the maximum. In this case, the throttle
curve must also be adjusted in the hover range.
Basic set-up procedure
Even though pitch and throttle curves can be set elec-
tronically over a wide range with the
mc-16 HoTT
and mc-20 HoTT transmitter, all linkage in the model
should already be mechanically pre-adjusted correctly
according to the instructions for the given helicopter.
Experienced helicopter pilots will be glad to help with
this basic set-up.
The carburettor linkage must be set so that the throttle
is just past the fully open setting with collective pitch
set to maximum or, for electric helicopters, with the
speed controller set to full. When the throttle limiter is
closed, however, it must be possible to just close off
the carburettor using the C1 trim lever (rapid throttle
setting of the “digital trim”, see page 58), without the
servo mechanically striking its end-stop. For electric
helicopters, it must be possible to cut the electric
motor’s speed controller safely with the throttle limiter
closed.
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